In paper packaging applications, it is desirable to provide barriers against water, oxygen, and carbon dioxide. Wettability of a paper surface can be reduced using sizing agents, while gas barriers can be formed by coating the paper with a continuous film of a suitable material. Examples of such barrier-producing films are paraffin wax, polyethylene, ethylene-vinyl acetate copolymer, and poly(vinylidene chloride) (PVDC). Of these, PVDC has the best water-, vapor-, and oxygen-barrier properties. Moreover, unlike other high oxygen-barrier materials, PVDC is almost insensitive to water. However, because of its high chlorine content, PVDC tends to corrode processing equipment, which increases manufacturing costs.
It would be an advantage in the art to prepare a non-chlorine-containing, self-dispersing latex or solution that can be used to make a coating that is effective as a barrier against small molecules. It would be further advantageous if the barrier properties were not adversely affected by contact with water. It would be desirable if the coating adhered to a substrate without the aid of an ancillary adhesive. Finally, it would be desirable for some applications that this coating be biodegradable, so that the product can be composted subsequent to its intended use.